1. Field of the Invention
The present invention relates to a fluid bearing device. This fluid bearing device is suitable for use as a bearing device in the spindle motor of an information apparatus, for example, a magnetic disc apparatus, such as an HDD or an FDD, an optical disc apparatus, such as a CD-ROM, a CD-R/RW, or a DVD-ROM/RAM, or a magneto-optical disc apparatus, such as an MD or an MO, the polygon scanner motor of a laser beam printer (LBP), a color wheel for a projector, or the small motor of an electric apparatus, such as an axial flow fan.
2. Related Background Art
Apart from high rotational accuracy, an improvement in speed, a reduction in cost, a reduction in noise, etc. are required of the motors as mentioned above. One of the factors determining such requisite performances is the bearing supporting the spindle of the motor. Recently, as such a kind of bearing, use of a dynamic pressure bearing superior in the above requisite performances is being considered or such a fluid bearing has been actually put into practical use. This type of fluid bearing is roughly classified into two categories: a dynamic pressure bearing equipped with a dynamic pressure generating means for generating dynamic pressure in a lubricant in a bearing clearance, and a circular bearing equipped with no such dynamic pressure generating means (a bearing whose bearing surface is of a circular configuration).
As an example of such a bearing device, JP 2000-291648 A discloses a dynamic pressure bearing device for use in the spindle motor of a disc drive apparatus, such as an HDD. In this bearing device, a bearing sleeve is fixed to the inner periphery of a housing formed as a bottomed cylinder, and a shaft member with a flange portion protruding radially outwards is inserted into the bore defined by the inner periphery of the bearing sleeve, wherein a fluid dynamic pressure is generated in a radial bearing clearance and a thrust bearing clearance formed between the rotating shaft member and the stationary members (the bearing sleeve, the housing, etc.), the shaft member being supported in a non-contact fashion by this fluid dynamic pressure.
Incidentally, a spindle motor of this type rotates a shaft member by an excitation force generated by a rotor magnet and a stator coil; conventionally, the rotor magnet is, in many cases, fixed to a member rotating with the shaft member (a disc hub or the like), whereas the stator coil is fixed to a metal bracket (a motor bracket) fixed to the outer periphery of the housing of a dynamic pressure bearing device.
The fixation of the motor bracket and the housing is generally effected by adhesion. Conventionally, the housing has been formed of a soft metal, such as brass; since the adhesion is effected between metal members, it has been possible to obtain a necessary and sufficient adhesive force.
Recently, however, use of a resin housing is being considered from the viewpoint of achieving a reduction in cost, etc. In this case, it is impossible to obtain a sufficient adhesive force for the connection between the resin housing and the motor bracket. Thus, what matters here is how to attain a sufficient adhesive force for the connection therebetween.